Effect of DMPA Content of Polyurethane Dispersion on Coating Properties

Polyurethane dispersions were synthesized from poly(neopentyl glycol adipate), isophorane diisocyanate (IPDI), and dimethylol propionic acid (DMPA) using conventional acetone process. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and particle size analysis were utilized to characterize the above-synthesized dispersion. The effect of DMPA contents were studied on glass transition temperature (Tg), particle size, stability, and gloss; as well as, the effect of pH on gloss and drying time was also studied. It was found that gloss was inversely proportional to particle size and pH.     

Self-healing biodegradable poly(urea-urethane) elastomers based on hydrogen bonding interactions

 Self-healing poly(urea-urethane)s (PUUs) showing a tolerance to mechanical damage are particularly desirable for high-performance elastomeric biomaterials. In this study a kind of biodegradable PUUs was synthesized from poly(ε-caprolactone) diol with L-lysine ethyl ester diisocyanate (LDI) extended with L-lysine ethyl ester dihydrochloride (LEED) in DMF and characterized by using ¹H-NMR, FTIR, DSC, XRD, SEM and tensile tests. Interestingly, they exhibited a self-healing characteristic upon exposure to 37℃ for as short as 30 min with the tensile strength keeping at 4.23 MPa and the elongation at break reaching to 627%. It is revealed that increasing the hard segment content in PUUs benefits the self-healing performance, and on the opposite increasing the soft segment content contributes to the biodegradability.     

Highly Stable Graphene Inks Based on Organic Binary Solvents

Formulating highly stable graphene-based conductive inks with consistency in electrical properties over the storage period has remained a significant challenge in the development of wearable electronics. Two highly stable graphene-based inks (Cyclohexanone:Ethylene glycol (CEG) ink and Cyclohexanone:Terpineol (CT) ink) are prepared by using two different organic binary solvents, for the first time, without using solvent exchange methods. Both the inks display remarkably high stability (stable even after two months) with negligible variability in electrical properties. Here, it is demonstrated how such inks can be utilized to coat flexible substrates to create wearable e-textiles. Both the inks coated e-textiles show significantly low sheet resistance (≈209.1 Ω □⁻¹ for CEG ink and ≈322.4 Ω □⁻¹ CT ink) that show less than a 15% increase in electrical resistance over two months. Therefore, these inks offer high productivity and reproducibility and can be one of the most effective methods for formulating graphene-based inks.     

Bio-based photo-curable polyurethane composites

Polyurethane (PU) covers a range of applications in wearable circuits, coating materials, foaming industries, surgical equipments, packing materials and replacement of plastic materials. As per broad applications spectrum, huge data on PU synthesis has been reported so far, with different types of polyols, isocyanates, organic acids, acrylates with different chain extenders, catalysts, emulsifiers and/or PI. In this review, for a comprehensive study of structure-activity relationship, data from last 5 years has been compiled for photo-curable PU categorized on the basis of solvent as well as acrylate components. In this review a range of parameters including tensile strength, hardness, flexibility, hydrophobicity/hydrophilicity, solvent resistance, storage/young's modulus, shape recovery, viscosity, curing kinetics and thermal stability has been compared against composition.